Volvo Trucks boosts safety on slippery winter roads

For trucks with trailers, slippery winter roads and downhill gradients represent a tough challenge for even the most skilled of drivers. There is always the risk of the rig becoming unstable and, in the worst-case scenario, starting to jack-knife. Volvo Trucks has now developed a solution that significantly improves safety.

"Even if the truck driver ultimately manages to control the situation, it can be extremely unpleasant both for oncoming road users and the truck driver, if a rig suddenly veers off its intended course on a downhill gradient," says Mats Sabelström, brake specialist for Volvo Trucks.

In order to minimise the risk of this type of situation and potential accidents, Volvo Trucks has developed a system known as Stretch Brake that automatically retards the trailer and straightens up the rig on slippery downhill stretches.

"About 15 percent of the total of 30,000 serious road accidents in Europe every year involve trucks, in a slightly declining trend1. With effective brakes, stability systems and collision warning systems we are already helping drivers avoid risky situations in difficult conditions. Stretch Brake is yet another important part of our long-term drive to increase traffic safety and minimise the number of accidents involving trucks," says Carl Johan Almqvist, Traffic and Product Safety Director at Volvo Trucks.

Stretch Brake is a complement to the rig's electronic stability program (ESP) - yet another system that Volvo Trucks was the first truck maker in the world to introduce. While ESP is at its most effective at higher speeds, Stretch Brake is only operational at speeds below 40 km/h. Both systems contribute to better stability and easier steering.

"One might call Stretch Brake a kind of low-speed ESP. As the rig approaches a downhill slope, the driver manually activates the system. When the driver then releases the accelerator, the brakes on the trailer are automatically applied in a pulsated mode all the way down the hill until the gradient levels out and speed can once again be increased," relates Mats Sabelström.

Stretch Brake was introduced in 2012 on Volvo FH trucks pulling drawbar trailers and in 2013 on Volvo FM trucks pulling drawbar trailers. In 2014 it will also become available for Volvo FH and FM semi-trailer rigs.

"Drivers who have tested Stretch Brake came away very impressed with the system. As we now also introduce the system on tractor-semitrailer rigs even more drivers will be able to negotiate difficult downhill gradients both more simply and safely," says Carl Johan Almqvist.

According to the Volvo Trucks Accident Research Team, which specialises in studying traffic safety, about 60 or so of the truck accidents that occurred in Sweden alone last year could have been avoided with Stretch Brake2.

Stretch Brake Facts

Increases safety on downhill gradients, especially on slippery roads and in curves.

Applies the drawbar brakes in a pulsating mode.

Straightens the rig, makes steering easier and reduces the risk of jack-knifing.

Operational at speeds below 40 km/h.

Introduced in 2012 on Volvo FH trucks and in 2013 on Volvo FM trucks. In 2014 it will also become available on tractor/semi-trailer rigs.

1 Source: CARE 2011, CARE is the European centralized database on road accidents which result in death or injury across the EU.2 Source: STRADA 2012, STRADA is a national (Swedish) information system collecting data of injuries and accidents in the entire road transport system. STRADA is based on information from the police as well as the hospitals.

“When you're driving, it is important that the trailer stays stable. In tough conditions, the Stretch Brake helps to keep the truck stable,” says Mats Sabelström, Brake Specialist for Volvo Trucks.

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“Even if you manage to avoid an accident it can be very unpleasant for both the truck driver and oncoming traffic if the truck skids off course while driving downhill,” says Mats Sabelström, brake specialist for Volvo Trucks.

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“Jack-knifing usually occurs in winter when roads are slippery. When it happens, it's a very scary feeling. It feels a bit like riding a roller coaster - you don’t have control of the vehicle,” says Johan Sundberg.

According to Volvo Trucks’ Accident Research Team, which researches traffic safety, around 60 of the accidents involving trucks that occurred in Sweden last year could have been avoided using Stretch Brake.

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Johan Sundberg runs Sundbergs haulage company and has been driving timber through forests for 20 years. Both he and his drivers experience jack-knifing from time to time.

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Mats Sabelström works as a brake specialist for Volvo Trucks and has been involved in developing the new Stretch Brake system.

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Test track Hällered, Sweden. Jack-knifing occurs when the trailer slides forward and swings out, facing a different direction than the truck. It can include several risks for oncoming traffic, the driver and the goods.

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Test track Hällered, Sweden. Jack-knifing occurs when the trailer slides forward and swings out, facing a different direction than the truck. It includes several risks for oncoming traffic, the driver and the goods.

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Test track Hällered, Sweden. Jack-knifing occurs when the trailer slides forward and swings out, facing a different direction than the truck. It includes several risks for oncoming traffic, the driver and the goods.

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The driver can activate the Stretch Brake system when driving on roads where there is a risk of jack-knifing, such as on downhill roads or on slippery, curvy roads.

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The Stretch Brake was introduced in 2012 on the Volvo FH and in 2013 on the Volvo FM truck. In 2014, the system will also be used for rigs with a tractor and trailer.

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When the driver brakes or just releases the accelerator pedal, there is a risk that the trailer slides forward and swings out, facing a different direction than the truck.

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When the Stretch Brake system is activated, it automatically applies pulsating pressure on the trailer’s brakes, causing the rig to stabilise.